Dryer for sheet material

ABSTRACT

This is a dryer for sheet material such as photographic prints and film which is particularly constructed to handle individual relatively large size prints and includes a walking beam transfer mechanism for transporting the sheets through the drying chamber with means for circulating warm air around and over the surfaces of the prints being dried in a manner to reduce the tendency of the sheet material to curl.

United States Patent [151 3,681,853

Reid 1. Aug. 8, 1972 [54] DRYER FOR SHEET MATERIAL v 3,47l, 1 34 'lO/1969 Cone ..263/6 A i [72] Inventor: Norman C. Reid, Minneapolis, i I

Minn. Primary Examiner-Carroll B. Dorlty, Jr.

' 1 At --J h W. Ad [73] Assignee: Pako Corporation, Minneapolis, mmey n4 mm v 57 ABSTRACT Wed: March 1971 This'is a dryer for sheet materialsuch as photographic [21] Appl. No.: 124,334 prints and film which isparticularly constructed to handle individual relatively large sizeprints and in- 52 us. Cl ..34/1s1 263/6 A dudes Walking beam transfermechanism trans 51 Int. Cl ..F2 6b 13/00 Porting the Sheets through thedrying with [58] Field of Search ..34/ 148, 151, 155, 162; means forcirculating warm air around and Over the 2 3 E, 6 A surfaces of theprints being dried in a manner to reduce the tendency of the sheetmaterial to curl.

[S 6] References Cited g UNITED STATES PATENTS I 5 Claims, 6 DrawingFigures 2,907,118 10/1959 Maescher ..34/ 155 i 33 33 :/L; voflla'Tfl'lm'ni'dlg" C ,z 2 2 23 u 22 h l 29 3 E' M I? l f r E s l2 g 3/I 2'6 25 j I: T T T 32 I i ::l l V -'t l H v 6i! int, l I q \1 /l DRYERFOR SHEET MATERIAL It has long been a problem in the drying ofphotographic prints and film to provide drying apparatus for individualseparate sheets which maintains goodcontrol over the sheets during thetransporting thereof individual sheets such as photographic prints andfilm and having a plurality of transversely spaced apart oscillatingtransfer elements in the form of a walking beam mechanism to transportthe sheets through the drying chamber and provided with means fordirecting warm air onto the surfaces of the sheets being dried in amanner to urge the sheets toward the transfer elements and reduce thetendency to curling of the shee without scratching the'top surfacesthereof.

It is still a furtherobject to provide a drying device for sheetmaterial whereby the device can be adjusted to vary the rate of travelthrough the drying chamber and thus vary the drying time and the feedingrollers are always driven at a speed which feeds the individual sheetsonto the transfer bed at a slower rate than the transfer mechanismcarries said sheets across the drying chamber regardless of theadjustment of the transport speed.

It is still a further specific object to provide a dryer the sheetsof'material'to be dried, and'feed; the same through the entrance opening13. Such a sheet S is illustrated in FIG. 2 as it is passing through therollers and 16. The surface of the rollers 15 and 16 issoft material,such as sponge rubber, in order to avoid damaging and scratching thesurface of the sheets being fed therethrough and only the hot air in theheating contacts the top surface of the sheets after delivery throughthe feeding rollers 15 and 16. Excess moisture is removed from thesheets and is collected on a drainage panel 17 which carries thecollected liquid out of the drying chamber and delivers it to acollection pan 18 in which the sheets to be dried may be stored transfermechanism which is adapted to transport the individual sheets to bedried through the drying chamber, without contacting the soft emulsionsurfaces such as those used with photographic prints and film, thusminimizing the possibility of scratching such surfaces during the dryingoperation.

These and other objects and advantages of this invention will beapparent from the following description made in connection with theaccompanying drawing wherein like reference characters refer to similarparts throughout the several views, and in which:

FIG. 1 is a side elevational view of the dryer with the cover closed;

FIG. 2 is a top plan view thereof with the cover removed and portionsbroken away;

FIG. 3 is a transverse vertical sectional view taken substantially alongthe line 3-3 of Fig. 1;

FIG. 3A is a transverse vertical section through one of the channelmembers 22 or 23 of the walking beam mechanism;

FIG. 4 is a central longitudinal sectional view taken substantiallyalong the line 4-4 of FIG. 2; and

FIG. 5 is a view similar to FIG. 4 taken substantially along the line5-5 of FIG. 2.

The dryer illustrated in the accompanying drawings embodies an outercasing designated as an entirety by the numeral 10, which has a cover 11which in the form shown is pivotally mounted as by the pivot rod 12. Thecasing and cover combine to form an enclosed drying chamber having anentrance opening 13 and a discharge opening 14 at opposite ends thereof.Two pairs of squeegee-type feeding rollers 15 and 16 receive priortobeing fed into the dryer. Suitable means for driving the squeegeerollers 15 and 16 are provided, such as the meshed worm gears 19 and 20,which are driven by a main drive shaft 21 which is driven by a motor Mwhich has a suitable speed control C.

A transfer bed is formed in the drying chamber by a walking beamtransport mechanism which receives the sheets S from the rollers 15 and16 and carries the same through the drying chamber and discharges saidsheets through the discharge opening 14 aftera predetermined timeinterval has elapsed. In the specific fonn shown, the walking beammechanism includes a plurality of parallel spaced apart stationarysupport members 22 and a plurality of oscillating transfer member 23which are interposed between the stationary channel members 22 and whichintermittently engage and transport the sheets S through the dryingchamber. Obviously, other transport mechanisms could be used whichcontact only one side of the sheets and which permit the flow of dryingair downwardly through the chamber. Both the support members 22 and thetransfer members 23 are coated with a suitable material which has lowthermal conductivity properties and which will also prevent thecorrosion of the members due to the chemical solutions used to processthe photographic sheets S. As best shown in FIG. 3A, a soft vinyl resinmaterial, respectively designated 22a and 23a, is applied to channelmembers 22 and 23 and has the foregoing coating properties. Thismaterial also has a higher friction coefficient than the metal channelmembers 22 and 23. Of course, other materials having the desiredproperties could be used also. The oscillatv ing members 23 are allmounted on a single oscillating frame structure 24 and an eccentricdriving mechanism 25 imparts the oscillating motion to said frame andthe transfer members 23. The oscillating members 23 travel in agenerally circular path which carries them up above the stationarymembers 22 during the forward portion of their movement and thus bringsthem into contact with the sheets during the sheet advancing portion ofthe oscillating path. As the members 23 are oscillated back during thereturn portion of the path, they drop down below the stationary memberswhich then support the sheets in stationary position until said sheetsare re-engaged by the driving members during the next forward advancingportion of their movement.

The eccentric drive mechanism embodies a pair of cross shafts 26 whichare driven by the maindrive shaft 21 as by the meshed gears 27. Aneccentric driving connection is made between the respective ends of theshafts 26 and the adjacent portion of the frame 24 as by pins 28 whichare eccentrically connected to rotary wheels 29 respectively mounted onshafts 26, as best shown in FIGS. 2 and 5. Slots 24a are provided in theframe 24 to receive the pins 28.

It is important that the transfer speed of the sheets S on the dryingbed is somewhat faster than the speed at which said sheets are fed ontothe bed by the feed rollers 15 and 16. This speed differential isestablished and maintained by the driving ratios of the gears 19 and 20i which drive said rollers and the gears 27 which drive the cross shafts26. When the driving speed of the motor M is varied the speed of thefeed rollers 15 and 16 and the speed of shafts 26 will be simultaneouslyvaried and the predetermined speed differential will be maintained.

A plurality of heating elements 30 are provided for heating the air anda blower 31 draws the air downwardly through the transfer bed and intocontact with the heating elements 30. The flow of air from the blower 31is divided substantially equally by a raised divider a formed on theinside of the bottom of housing 10. A center heating element 30 ismounted above the divider 10a and combines with the two outer heatingelements to heat the air circulated downwardly from the blower 31.Substantially equal volumes of air are circulated through the outerconduit passages 32 which deliver the heated air into the drying chamberfrom opposite sides thereof in order to substantially balance the flowof air into the upper portion of the chamber which then flows downwardlyonto the sheets and through the transfer bed to be heated andrecirculated. A plurality of spoilers or air directing baffles 33 may beprovided on the inside of the cover 11 to direct the air dischargedthrough the passages 32 generally downwardly.

It will be seen that I have provided a relatively simple, yet highlyefficient, dryer for individual sheets such as photographic prints orfilm, including a transport mechanism which combines with the balancedair flow circulated primarily in a downward direction through the dryingchamber to maintain a positive air pressure on the top surface of thesheets S and a partial vacuum on the bottom surface to increase drivingcontact with said oscillating transport mechanism while at the same timetending to prevent curling of the sheets. The intermittent contact ofthe sheets with the stationary and oscillating support members producesa constantly varying random contact area between the bottom side of thesheets being dried and the members 22 and 23 so that the thermalconduction between a specific area of the surface of the support membersis minimized. The low thermal conductivity of the coating on both thestationary and oscillating members 22 and 23 combines with the constantvarying random contact area of said members with the sheets being driedto produce uniform drying of the entire surface of the sheets. Thiseliminates streaking of the photographic surface which is frequently aproblem with uneven drying. The transport mechanism does not require anypositive contact with the upper surface of the sheets other than theforce of the air pressure which gently presses downwardly thereon asdescribed. This eliminates any possibility of scratching the relativelysoft upper surface of photographic prints or film while rt be ci ursefheunderstood that various changes may be made in the form, details,arrangement and proportion of the parts without departing from the scopeof this invention which generally stated consists in the manner setforth in the appended claims.

What is claimed is:

l. A dryer for flexible sheet material such as photographic prints andfilm, said dryer comprising a drying chamber with a sheet inlet openingand a sheet discharge opening therein,

a substantially horizontal walking beam transpo mechanism having spacedtransfer members to permit the flow of heated air downwardlytherethrough and including a plurality of moving transfer membersengaging only the bottom side of the sheet material to be dried totransport the same through said drying chamber,

means for supplying heated air to the top surface of said sheets to bedried to combine with weight of the sheets to form the only externalforces urging said sheets downwardly into contact with the movingtransfer members, and

feeding means for delivering the sheet material through said inletopening on to said transfer members at a speed slower than the speed atwhich said sheets are moved across the transport mechanism by saidtransfer members.

2. Structure set forth in claim 1 and means for varying the speed withwhich said sheets are transferred through said drying chamber.

3. The structure set forth in claim 1 and a pair of opposed airdirecting passages located on opposite sides of said drying chamber anddirecting heated air into the upper portion of said chamber through saidopposed passages whereby the flow of air will be directed primarilydownwardly to maintain contact between the sheets and the members ofsaid transport mechanism.

4. The structure set forth in claim 1 and said bed including a pluralityof spaced stationary support members interposed in laterally spacedrelation between said moving transfer members, said moving memberslifting said sheets out of engagement with the stationary members andsubsequently re-depositing said sheets on the stationary members at anadvanced position toward the discharge end of said drying chamber, thesheets being dried being free and unconfined in said chamber to produceconstantly varying random contact areas between the lower surface of thesheets and the members of said transport mechanism.

5. The structure set forth in claim 1 and said transport mechanismmembers being constructed so that at least the area of contact thereofwith the sheets is of a material having a low coefficient of heatconductivity to minimize localized heat transfer between the members ofsaid transport mechanisms and the engaged portions of the sheets.

1. A dryer for flexible sheet material such as photographic prints andfilm, said dryer comprising a drying chamber with a sheet inlet openingand a sheet discharge opening therein, a substantially horizontalwalking beam transport mechanism having spaced transfer members topermit the flow of heated air downwardly therethrough and including aplurality of moving transfer members engaging only the bottom side ofthe sheet material to be dried to transport the same through said dryingchamber, means for supplying heated air to the top surface of saidsheets to be dried to combine with weight of the sheets to form the onlyexternal forces urging said sheets downwardly into contact with themoving transfer members, and feeding means for delivering the sheetmaterial through said inLet opening on to said transfer members at aspeed slower than the speed at which said sheets are moved across thetransport mechanism by said transfer members.
 2. Structure set forth inclaim 1 and means for varying the speed with which said sheets aretransferred through said drying chamber.
 3. The structure set forth inclaim 1 and a pair of opposed air directing passages located on oppositesides of said drying chamber and directing heated air into the upperportion of said chamber through said opposed passages whereby the flowof air will be directed primarily downwardly to maintain contact betweenthe sheets and the members of said transport mechanism.
 4. The structureset forth in claim 1 and said bed including a plurality of spacedstationary support members interposed in laterally spaced relationbetween said moving transfer members, said moving members lifting saidsheets out of engagement with the stationary members and subsequentlyre-depositing said sheets on the stationary members at an advancedposition toward the discharge end of said drying chamber, the sheetsbeing dried being free and unconfined in said chamber to produceconstantly varying ''''random'''' contact areas between the lowersurface of the sheets and the members of said transport mechanism. 5.The structure set forth in claim 1 and said transport mechanism membersbeing constructed so that at least the area of contact thereof with thesheets is of a material having a low coefficient of heat conductivity tominimize localized heat transfer between the members of said transportmechanisms and the engaged portions of the sheets.